Catalytic reactor and vehicle equipped with said catalytic reactor

ABSTRACT

A catalytic reactor includes a catalytic reaction section, which has a purification catalyst for gas purification, and a warming-up section, which is located at a position capable of heat-exchanging with the purification catalyst and has a chemical heat storage material that generates heat when ammonia is fixed and absorbs heat when ammonia is desorbed. The catalytic reactor is further includes an ammonia supply section, which has an adsorbent capable of adsorbing ammonia and transfers ammonia to and from the warming-up section through the adsorption and desorption of the ammonia, and an ammonia depressurization section, which has an ammonia fixation section for fixing ammonia and reduces the partial ammonia pressure of at least the interior of the warming-up section after ammonia is desorbed from the chemical heat-storage material.

FIELD OF THE INVENTION

The present invention relates to a catalytic reactor utilizing achemical heat storage material and a vehicle equipped with the catalyticreactor.

BACKGROUND OF THE INVENTION

In recent years, the emission reduction of carbon dioxide as a part ofthe global environmental preservation has been strongly demanded, andstudies on technologies of the energy saving and the promotion ofexhaust heat utilization are being extensively made. As one examplethereof, technologies of highly efficiently storing heat are beingstudied. One example of such technologies is chemical heat storagetechnologies having a large heat storage quantity per unit volume orunit mass and being capable of storing heat for a long period.

One example of such chemical heat storage technologies is technologiesof fixing ammonia on a metal salt. For example, Patent Document 1 statesthat when a chloride of an alkaline earth metal or a chloride of atransition metal occludes ammonia, heat is generated, and when ammoniais discharged, heat is absorbed. Patent Document 1 states as a specificexample thereof a chemical heat storage apparatus equipped with a solidphase reactor and a condenser connected to the solid phase reactor. Inthe interior of the solid phase reactor, an ammine complex of a metalchloride is charged. Ammonia gas is released from the ammine complex ofthe metal chloride by supply of a heating source. The solid phasereactor holds the pressure of the ammonia gas. The condenser condensesthe ammonia gas by supply of cooling water.

Further, for example, Patent Document 2 discloses a catalyst warming-upapparatus for warming-up a purification catalyst of a purificationapparatus for exhaust gas by utilizing the following reversiblereaction, and carrying out an exothermic reaction by supplying water tocalcium oxide under a low-temperature environment.

CaO+H₂O

Ca(OH)₂ +Q  (reversible reaction)

PRIOR ART DOCUMENTS Patent Documents

-   Patent Document 1: Japanese Laid-Open Patent Publication No.    6-109388-   Patent Document 2: Japanese Laid-Open Patent Publication No.    59-208118

Non-Patent Document

-   Non-Patent Document: Bull. Chem. Soc. Jpn. 77 (2004) 123

SUMMARY OF THE INVENTION

Among the above-mentioned conventional technologies, however, thechemical heat storage apparatus needs to have a mechanism to control thegas/liquid phase change because the chemical heat storage apparatus isequipped with a condenser to condense ammonia gas. The apparatus istherefore likely to become complicated.

The catalyst warming-up apparatus, since needing water, is difficult tooperate below the freezing point. Heat is necessary that equates to atemperature of 400° C. or higher for the regeneration reaction(CaO+H₂O←Ca(OH)₂+Q) of calcium oxide after the warming-up. If the heatis intended to be obtained from exhaust gas from an internal combustionengine (hereinafter, engine), a long time is necessary. The regenerationis not completed depending on the operation state, and the warming-up ofthe purification catalyst may possibly not be carried out at thesucceeding starting time.

Technologies of fixing ammonia to a metal chloride are known asdescribed above. In the case of employing a warming-up method ofutilizing an exothermic reaction when ammonia is fixed by adsorption orthe like, since ammonia is hardly frozen even below the freezing point,the regeneration at a starting time and at a low-temperature time ispossible. However, since ammonia is liable to be pyrolyzed into hydrogenand nitrogen when being exposed to a high temperature of 400° C. orhigher, there is a fear that the warming-up function cannot bemaintained stably.

For example, in vehicles equipped with a diesel engine or the like,exhaust gas discharged from their engine usually contains, in additionto nitrogen oxides (NO_(x)), carbon monoxide (CO), hydrocarbons (HC) andthe like, particulate matter (hereinafter, abbreviated to PM in somecases) containing as main components carbonaceous substances including asoluble organic fraction (SOF), which is cinder of soot, fuel and engineoil. Therefore, purification of exhaust gas by a filter (DPF: Dieselparticulate filter; hereinafter, DPF) is carried out by equipping thevehicles with the filter to reduce the particulate substances in theexhaust gases. An example of the DPF includes DPF catalysts in which anoble metal is supported on a base material. PM deposited on a DPF isremoved by a combustion treatment at a high temperature reaching 400° C.or higher. Therefore, in an exhaust system equipped with a DPF, sincethe pyrolysis of ammonia is easily caused as described above,application of a chemical heat storage apparatus utilizing ammonia isdifficult.

It is an object of the present invention to provide a catalytic reactorhaving a warming-up function that stably operates while preventingpyrolysis of ammonia, and develops a high catalytic activityirrespective of the usage temperature environment, and also provide avehicle that stably carries out purification of its exhaust gasirrespective of the usage temperature environment.

The present invention has been achieved based on the following findings.That is, if exothermic and endothermic reactions when ammonia isadsorbed to and desorbed from a chemical heat storage material areutilized, the warming-up function can be maintained even under alow-temperature environment. However, there is a case where ammonia isexposed to a high temperature, for example, in an exhaust systemcarrying out a high-temperature treatment in order to remove PM, such asin a diesel engine. For example, at the PM treatment of a diesel engine,the temperature of its exhaust gas reaches 400° C. or higher. In such atemperature range, ammonia is pyrolyzed, and the initial warming-upfunction cannot continuously be maintained in some cases. The warming-upis usually carried out by heat generation by adsorption of ammonia to achemical heat storage material. After the warming-up termination,ammonia is recovered for preparation for the succeeding warming-up, andthe chemical heat storage material is regenerated to a state of havingdesorbed ammonia, thereby enabling to carry out repeatedly thewarming-up. It is important from the viewpoint of retaining thewarming-up function for a long period that ammonia remaining in thesystem including the piping is previously separated from ahigh-temperature region, that is, the pressure of ammonia in the systemexposed to a high temperature is reduced. After the warming-up, sincethe difference in magnitude of the ammonia pressure between differentplaces in the system in which ammonia is flowed is low, ammonia islikely to easily remain in the piping and the like. Therefore, it iseffective to install an ammonia fixation material developing a highammonia adsorption capacity even at a low temperature and being capableof removing ammonia remaining in the system by adsorption.

To achieve the foregoing objective and in accordance with one aspect ofthe present invention, a catalytic reactor is provided that includes acatalytic reaction section, a warming-up section, an ammonia supplysection, and an ammonia depressurization section. The catalytic reactionsection has a purification catalyst for purifying gas. The warming-upsection is located at a position capable of heat-exchanging with thepurification catalyst. The warming-up section has a chemical heatstorage material that generates heat when ammonia is fixed and absorbsheat when ammonia is desorbed. The ammonia supply section has anadsorbent capable of adsorbing ammonia. The ammonia supply sectiontransfers ammonia from and to the warming-up section by adsorption anddesorption of ammonia. The ammonia depressurization section has anammonia fixation section for fixing ammonia and reduces an ammoniapartial pressure at least in the warming-up section after the desorptionof ammonia from the chemical heat storage material.

In the catalytic reactor, the catalytic reaction section provided withthe purification catalyst to purify exhaust gas discharged from aninternal combustion engine is equipped with the warming-up section usingthe chemical heat storage material to absorb and generate heat byadsorption and desorption of ammonia. The purification catalyst iswarmed up by the warming-up section to thereby improve the catalyticactivity under a low-temperature environment (including below thefreezing point). The catalytic reactor is provided further with theammonia supply section to desorb ammonia when the purification catalystis warmed up by the warming-up section, and to adsorb ammonia forpreparation for the succeeding warming-up after the warming-up, and theammonia depressurization section to reduce the ammonia pressure bychemically or physically adsorbing ammonia that has not been completelyadsorbed and recovered by the ammonia supply section when ammonia wasadsorbed for preparation for the warming-up and remains in thewarming-up section, the piping and the like. Although when thetemperature of a catalyst is normal temperature (25° C.) or lower, thecatalytic activity to exhaust gas would be usually insufficient, thewarming-up function can thereby be maintained stably. The catalyticreaction section is thereby heated (for example, to about 150° C.) andthe catalytic activity is highly maintained and the purificationfunction to the exhaust gas is improved. After warming-up, as seen inthe purification mode of DPF installed for PM removal in automobilesmounting a diesel engine, exhaust gas of a high temperature reaching400° C. or higher is discharged from an internal combustion engine insome cases. If ammonia is exposed to exhaust gas of such a hightemperature, ammonia is pyrolyzed and the initial warming-up functioncannot be retained in some cases. In the catalytic reactor according tothe present invention, however, ammonia adsorbed to the chemical heatstorage material of the warming-up section is gradually desorbed andreturns to the ammonia supply section as the chemical heat storagematerial of the warming-up section is heated by the temperature rise ofthe exhaust gas after the warming-up, and ammonia remaining in thewarming-up section and the piping is further separated by the ammoniadepressurization section. Minimization of pyrolysis of ammonia used forwarming-up is thereby achieved.

As described above, in the catalytic reactor according to the presentinvention, the use of ammonia as a medium for heat transport ensures astable warming-up function under a low-temperature environment(including below the freezing point), and prevents the pyrolysis ofammonia when the catalytic reactor is applied to a gas flow system inwhich a high-temperature gas to be purified is flowed. Therefore, theuse of the catalytic reactor according to the present invention canconstruct a catalytic purification system capable of stably developingan exhaust gas purification function using a catalyst.

In accordance one embodiment, the adsorbent of the ammonia supplysection is preferably a physical adsorbent capable of physicallyadsorbing ammonia. The use of the physical adsorbent can make small theheat quantity necessary for fixation and desorption of ammonia, and canmake the adsorption and desorption of ammonia to be easily carried outwith lower energy.

In accordance with one embodiment, the warming-up section preferably hasat least one ammonia supply port and a porous body member arrangedbetween the chemical heat storage material and the ammonia supply port,and the porous body member is preferably arranged such that ammoniasupplied to the warming-up section through the at least one ammoniasupply port diffuses in the porous body member and contacts the chemicalheat storage material.

One or more of ammonia supply ports for supplying ammonia are provided,and when ammonia is supplied to the chemical heat storage materiallocated in the warming-up section, the warming-up of a catalyst isstarted by the exothermic reaction accompanying the chemical adsorptionof ammonia to the chemical heat storage material. At this time, sincethe porous body member having a large number of gas-diffusible pores isprovided between the ammonia supply ports and the chemical heat storagematerial, ammonia is flowed and diffused through the porous body memberand supplied to the chemical heat storage material. Hence, theexothermic reaction in the chemical heat storage material can uniformlybe caused across the broad range.

In one embodiment, the ammonia fixation section is preferably formed byusing a chemical heat storage material to generate heat when ammonia isfixed and to absorb heat when ammonia is desorbed.

The ammonia fixation section of the ammonia depressurization sectionhas, for example, a function of removing ammonia gas remaining in thewarming-up section and in the piping between the warming-up section andthe ammonia supply section, and reducing the ammonia pressure (partialpressure). The ammonia fixation section is preferably formed by using achemical heat storage material. The chemical heat storage materialpreferably has a higher adsorption capacity of ammonia than that of anadsorbent of the ammonia supply section, and easily chemically adsorbammonia in a lower temperature range than the chemical heat storagematerial of the warming-up section. Further providing such an ammoniafixation section separately from the ammonia supply section enables toreduce the pressure of ammonia remaining in the warming-up section andthe piping after the warming-up.

In one embodiment, the chemical heat storage material preferablycontains at least a metal chloride. More preferably, the metal chlorideis selected from the group consisting of alkali metal chlorides,alkaline earth metal chlorides and transition metal chlorides.

Metal chlorides are suitable in the point of being capable of providinga high heat storage density (kJ/kg). The use of a metal chlorideenhances the warming-up function of the purification catalyst. Alkalimetal chlorides, alkaline earth metal chlorides, and transition metalchlorides are useful in the point of more enhancing the warming-upfunction.

The heat storage density indicates a heat quantity (kJ) absorbed perkilogram of a metal chloride by desorption of ammonia.

In one embodiment, the ammonia supply section can contain a physicaladsorbent selected from the group consisting of activated carbon,mesoporous silica, zeolite, silica gel, and clay minerals.

Activated carbon, mesoporous silica, zeolite, silica gel or a claymineral, which is a physical adsorbent, exhibits a smaller heat quantitynecessary for the desorption or adsorption of 1 mole of ammonia thanthat of the chemical adsorption material when desorbing ammonia to beintroduced to the warming-up section, or again adsorbing ammoniadesorbed from the warming-up section after the warming-up termination.Therefore, transfer of ammonia can be carried out in a smaller heatquantity.

In accordance with one embodiment, the chemical heat storage materialpreferably contains at least one of MgCl₂, MnCl₂, CoCl₂, NiCl₂, MgBr₂and MgI₂. The ammonia fixation section of the ammonia depressurizationsection preferably has a chemical heat storage material that generatesheat when ammonia is fixed and absorbs heat when ammonia is desorbed.The second chemical heat storage material contains at least one ofBaCl₂, CaCl₂, and SrCl₂.

MgCl₂, MnCl₂, CoCl₂, NiCl₂, MgBr₂ or MgI₂ provides a high heat storagedensity (kJ/kg), and is useful in the point of enhancing the warming-upfunction, and BaCl₂, CaCl₂ or SrCl₂ easily desorbs fixed ammonia and cansupply ammonia to the warming-up section at a lower temperature.

In accordance with one embodiment, the ammonia depressurization sectionpreferably has a heating section that heats the ammonia fixation sectionby heat-exchanging with the ammonia fixation section through flow of aheat medium.

Carrying out of the temperature control of the ammonia fixation sectionthrough the flow of the heating medium allows the rapid temperaturecontrol. The separation and removal of ammonia remaining in thewarming-up section and the piping is thereby rapidly carried out.

In accordance with another aspect of the present invention, a vehicle isprovided that includes an internal combustion engine and a catalyticreactor that is adapted such that exhaust gas discharged from theinternal combustion engine flows into the catalytic reactor.

In the vehicle, since the exhaust gas discharged from the internalcombustion engine is delivered to the catalytic reactor according to thepresent invention and is purified, the purification function can stablybe developed even when the usage environment is a low-temperature range(including below the freezing point). The removal of the exhaust gasdischarged from the vehicle is thereby carried out at a high efficiency.

In accordance with one embodiment, the internal combustion engine is adiesel engine, and the vehicle further includes a carbonaceous substancepurification section (for example, DPF) downstream of the catalyticreactor in an exhaust gas flow direction. The carbonaceous substancepurification section reduces particular matter (PM) in exhaust gas.

In the carbonaceous substance purification section, since PM isdeposited. The PM is also deposited on the filter wall surface and flowsinto the interior of the wall to be accumulated. This makes one cause ofclogging pores of the filter, there is a case where exhaust gas of ahigh temperature of 400° C. or higher is flowed and the DPF regenerationmode for removing the PM is carried out. For such a case, since thecatalytic reactor with which the vehicle according to the presentinvention is equipped prevents ammonia used at the warming-up from beingexposed to a high temperature of about 400° C., and prevents the ammoniafrom being pyrolyzed to hydrogen and nitrogen, the warming-up functioncan stably be maintained over a long period.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a part of a thermal system of anautomobile mounting a catalytic reactor having a warming-up functionaccording to one embodiment of the present invention;

FIG. 2 is a schematic diagram showing one example of the catalyticreactor of FIG. 1;

FIG. 3 is a schematic perspective view specifically showing one exampleof the gas purifier of FIG. 1;

FIG. 4 is a graph showing relationships between the heat storagetemperature and the heat storage density in each compound;

FIG. 5 is a schematic diagram showing the catalytic reactor of FIG. 1carrying out warming-up by introducing ammonia gas at a cold start;

FIG. 6 is a schematic diagram showing a flow of ammonia gas afterwarming-up in the catalytic reactor of FIG. 1;

FIG. 7 is a schematic diagram showing the catalytic reactor of FIG. 1from which remaining ammonia is being removed by an NH₃ depressurizationheat storage reactor;

FIG. 8 is a schematic diagram showing a valve state of the catalyticreactor of FIG. 1 in a DPF regeneration mode;

FIG. 9 is a schematic diagram showing the catalytic reactor of FIG. 1 inwhich ammonia desorbed from the NH₃ depressurization heat storagereactor is returned to an NH₃ adsorption-desorption apparatus to therebycomplete regeneration; and.

FIG. 10 is a flowchart showing a warming-up control routine of thecatalytic reactor of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, by reference to FIGS. 1 to 10, one embodiment of thecatalytic reactor and the vehicle equipped therewith according to thepresent invention will be described. However, the present invention isnot limited to the embodiment described below.

In the present embodiment, a thermal system of an automobile as avehicle to which a catalytic reactor 20 having a warming-up function isapplied will first be described simply, and then, the catalytic reactor20 mounted on the automobile will be described in detail.

As shown in FIG. 1, an automobile according to the present embodiment isprovided with a diesel engine 10, which is an example of an internalcombustion engine, a catalytic reactor 20 for purifying exhaust gasdischarged from the diesel engine 10, and a PM removal filter (DPF:Diesel particulate filter) 80, which is a carbonaceous substance removalsection for removing carbonaceous particulate substances (PM) containedin the exhaust gas, in order in the exhaust direction of the exhaustgas. The diesel engine 10, the catalytic reactor 20 and the like areelectrically connected to a controller 100.

The automobile according to the present embodiment is equipped with thediesel engine 10. PM in the exhaust gas from the diesel engine 10 isdeposited on the DPF. During the PM removal from the DPF, the catalyticreactor 20 is exposed to a high-temperature environment of 400° C. orhigher by the flow of the exhaust gas of a high temperature reaching400° C. or higher. As described later, when the catalytic reactor 20 isequipped with a warming-up function using ammonia, there is a fear thatammonia is exposed to a high-temperature environment and pyrolyzed. Thecatalytic reactor 20 according to the present embodiment is, asdescribed later, equipped with an NH₃ depressurization heat storagereactor. Since in the catalytic reactor 20, ammonia is therefore notexposed to a high-temperature environment, the catalytic reactor 20 canretain an ammonia partial pressure in the reactor, that is, a warming-upfunction, over a long period.

For the PM removal filter (DPF) 80, a base material for DPF or a DPFcatalyst composed of a base material for DPF and a catalytic metalsupported thereon is usually used. One example of the DPF is a catalystcomposed of a porous wall material such as a honeycomb base materialcomposed of cordierite, silicon carbide, a metal or the like, andcatalytic particles supported on the interior or the surface of the wallmaterial. The catalytic particle is composed of a noble metal such asplatinum (Pt), palladium (Pd) or rhodium (Rh), and a carrier carryingthe noble metal.

As shown in FIG. 2, a catalytic reactor 20 is equipped with a gaspurifier 30 for purification of exhaust gas having a purificationcatalyst and a warming-up heat storage reactor, which is a warming-upmechanism, an NH₃ adsorption-desorption apparatus 60, which is oneexample of an ammonia supply section capable of adsorbing and desorbingammonia gas (hereinafter, abbreviated to NH₃ in some cases), and an NH₃depressurization heat storage reactor 70, which is an ammonia pressurereduction section for reducing the ammonia pressure in the apparatusesand pipes by removing ammonia gas (remaining ammonia) remaining in theapparatuses and piping by adsorption.

In the temperature range of normal temperature (for example, 25° C.) orlower, the catalytic activity of a purification catalyst for purifyingexhaust gas is usually low. Hence, when the temperature of the exhaustgas is low, for example, at the time of engine starting and during theengine operation after the engine starting and until the temperature ofthe exhaust gas rises, a desired purification performance cannot beattained in some cases. This becomes remarkable particularly when theengine is started under a low-temperature environment such as below thefreezing point, and in other cases. The catalytic reactor 20 accordingto the present embodiment is equipped with the warming-up mechanismusing ammonia as a warming-up mechanism to previously warm up thepurification catalyst. Hence, the catalytic activity is highlymaintained even in a low-temperature environment, and the gaspurification is promoted. Particularly the warming-up heat storagereactor, which is a warming-up mechanism, since utilizing an exothermicreaction accompanying adsorption of ammonia as described below insteadof an exothermic reaction utilizing water, can utilize the exothermicreaction even in an environment below the freezing point. Further, thecatalytic reactor 20, which is equipped with the NH₃ depressurizationheat storage reactor 70, can remove ammonia remaining in the apparatusessuch as the warming-up heat storage reactor and the piping from theapparatuses and piping. Even when the warming-up heat storage reactorreaches a high temperature of 400° C. or higher, the pyrolysis ofammonia contributing to warming-up, and a decrease in the warming-upfunction accompanying the pyrolysis are thereby prevented.

The gas purifier 30 is equipped with a catalytic reaction apparatus 40,which is one example of a catalytic reaction section for purifying theexhaust gas by the built-in purification catalyst, and the warming-upheat storage reactor 50, which is one example of a warming-up sectionhaving a warming-up function of the purification catalyst.

The catalytic reaction apparatus 40 is equipped with a honeycombmonolith base material 42 to form a honeycomb structure as a supportbase material, and a catalyst layer provided on the support basematerial. In the catalyst layer, catalyst particles are supported oncarriers. When exhaust gas is introduced to the catalytic reactionapparatus 40, gas components such as HC and CO in the exhaust gas aredecomposed by the purification catalyst, and removed from the exhaustgas. Specific examples of the support base material include SiChoneycomb base materials, cordierite honeycomb base materials, and metalhoneycomb base materials. Examples of the catalyst particle includeparticles of noble metals such as platinum (Pt), palladium (Pd), andrhodium (Rh). The carrier carrying the particles includes particles ofoxides such as zirconium dioxide (ZrO₂), aluminum oxide (Al₂O₃), silica,silica-alumina, ceria (CeO₂), and zeolite.

In the catalytic reaction apparatus 40, a temperature detection sensor44 for detecting the temperature of the catalyst layer is attached, andthe temperature of the catalyst can be detected at the warming-up or thelike.

As shown in FIG. 2, the warming-up heat storage reactor 50 is arrangedto cover the outer peripheral surface of the catalytic reactionapparatus 40 to be able to heat-exchange with the purification catalystin the catalytic reaction apparatus 40. FIG. 3 shows a specificstructure of the warming-up heat storage reactor. As shown in FIG. 3,the warming-up heat storage reactor 50 is provided with a plurality ofplat-like heat storage materials 52 arranged along the outer peripheralsurface of the honeycomb monolith base material 42 of the catalyticreaction apparatus 40, and a porous body member 54 covering over theplurality of heat storage materials 52 and spaces between the heatstorage materials (that is, the outer peripheral surface of the basematerial 42). An armor material 56 is arranged on the periphery of theporous body member 54 so as to cover the entire surface of the porousbody member; and to the armor material 56, an NH₃ inlet port 58, whichis an ammonia supply port for introducing ammonia gas (NH₃), isattached. That is, the porous body member 54 is arranged between theheat storage materials 52 and the NH₃ inlet port 58. In the porous bodymember 54, flow paths are formed through which NH₃ passes through poresof the porous body member 54 and is able to flow.

When NH₃ is introduced from the NH₃ inlet port 58, the introduced NH₃flows in the porous body member 54 and reaches the positions of theplurality of heat storage materials 52. Thereby, the plurality of heatstorage materials 52 contact NH₃. At this time, NH₃ reacts with each ofthe heat storage materials 52. The reaction is an exothermic reactionaccompanying the adsorption of NH₃, and the generated heat is utilizedfor warming-up of the catalyst.

The heat storage material 52 is formed into a plate shape by pressing apowder of magnesium chloride (MgCl₂), which is a chemical heat storagematerial. In the present embodiment, as shown in FIG. 3, the heatstorage material 52 is constituted by arranging plate-like molded bodiesof the heat storage material. However, the heat storage material 52 maybe arranged as a single continuous layer on the entire surface along theouter peripheral surface of the honeycomb monolith base material 42.

The warming-up heat storage reactor 50 according to the presentembodiment is provided with MgCl₂ (magnesium chloride) as a chemicalheat storage material. The reaction between magnesium chloride andammonia is the following reversible reaction (1), and the warming-up ofthe purification catalyst can be repeatedly carried out according to thereaction, in accordance with to requirements. That is, when the reactionproceeds in the right direction in the following reversible reaction(1), ammonia is fixed (adsorbed) on the heat storage material, and theheat generation is caused. When the reaction proceeds in the leftdirection in the following reversible reaction (1), ammonia is desorbedfrom the heat storage material, and the heat absorption is caused.

MgCl₂.2NH₃+4NH₃

MgCl₂.6NH₃ +Q ¹[kJ]  (1)

The chemical heat storage material is not limited to MgCl₂, and acompound generating an exothermic reaction at the adsorption of ammoniacan be applied. The chemical heat storage material is, from theviewpoint of enhancing the heat storage density in the reactor,preferably metal chlorides, metal bromides, and metal iodides. Thechemical heat storage material is more preferably, for example, alkalimetal chlorides, alkaline earth metal chlorides, transition metalchlorides, alkali metals bromide, alkaline earth metal bromides,transition metal bromides, alkali metal iodides, alkaline earth metaliodides, and transition metal iodides, and is particularly preferablyLiCl, MgCl₂, CaCl₂, SrCl₂, BaCl₂, MnCl₂, CoCl₂, NiCl₂, MgBr₂, or MgI₂.The metal chlorides, metal bromides and metal iodides may be used singlyor in combinations of two or more.

FIG. 4 shows, for each compound of LiCl, MgCl₂, CaCl₂, SrCl₂, BaCl₂,MnCl₂, CoCl₂, NiCl₂, MgBr₂, and MgI₂, a relationship between the heatstorage temperature (° C.) and the heat storage density (kJ/kg). Theheat storage temperature (° C.) indicates one example of a temperatureat which ammonia can be desorbed. The heat storage density (kJ/kg)indicates a heat quantity (kJ) capable of being absorbed by desorptionof ammonia per kilogram of the each compound. As shown in FIG. 4, LiCl,MgCl₂, CaCl₂, SrCl₂, BaCl₂, MnCl₂, CoCl₂ and NiCl₂ indicate high heatstorage densities of about 800 kJ/kg to 1,470 kJ/kg. The heat storagetemperature depends on the kind of the compound, and is in the range ofabout 30° C. to 300° C.

In the present embodiment, the kind of the compound can suitably beselected according to the desired ammonia pressure and temperature.Therefore, the breadths of the ammonia pressure and temperature beingable to be selected according to an object of the heat utilization aremade large. For example, when the adsorption temperature of ammonia isdesired to be made low, BaCl₂, CaCl₂ or SrCl₂ can be selected. Incontrast, when the adsorption temperature of ammonia is desired to bemade relatively high, MgCl₂, MnCl₂, CoCl₂, NiCl₂, MgBr₂, or MgI₂ can beselected.

A molding method is not particularly limited. A known molding methodsuch as pressure molding or extrusion is applicable to, for example, aheat storage material (or a slurry containing the heat storage material)containing a chemical heat storage material and, as required, othercomponents such as a binder. The pressure at the molding can be made tobe, for example 20 to 100 MPa, and is preferably 20 to 40 MPa.

In the interior of the NH₃ adsorption-desorption apparatus 60, anactivated carbon as a physical adsorbent to adsorb ammonia is provided.The NH₃ adsorption-desorption apparatus 60 communicates with thewarming-up heat storage reactor 50 through an NH₃ flow pipe 62 throughwhich NH₃ is flowed. The NH₃ adsorption-desorption apparatus 60, at thewarming-up of the purification catalyst, discharges ammonia gas andsupplies the ammonia gas to the warming-up heat storage reactor 50, andafter the warming-up termination, again adsorbs ammonia gas dischargedfrom the warming-up heat storage reactor 50 and recovers the ammoniagas. In such a manner, the NH₃ adsorption-desorption apparatus 60transfers ammonia to and from the warming-up heat storage reactor 50.

The use of an adsorbent capable of adsorbing ammonia reduces the heatquantity necessary for the fixation and desorption of ammonia, and thuscan make ammonia to be easily adsorbed and desorbed in a lower energy.For example, while the heat quantity necessary for the fixation anddesorption of 1 mole of ammonia is 40 to 60 kJ/mol for a chemical heatstorage material (for example, LiCl, MgCl₂, CaCl₂, SrCl₂, BaCl₂, MnCl₂,CoCl₂, NiCl₂, MgBr₂ or MgI₂), that can be suppressed to 20 to 30 kJ/molfor the physical adsorbent.

As shown in FIG. 2, in the present embodiment, the NH₃adsorption-desorption apparatus 60 communicates with the warming-up heatstorage reactor 50 through the NH₃ flow pipe 62. If there aredifferences in ammonia pressure between the NH₃ adsorption-desorptionapparatus 60, and the warming-up heat storage reactor 50 and the NH₃flow pipe 62, the pressure differences can flow ammonia gastherebetween. For example, when the purification catalyst is warmed up,the ammonia partial pressure in the NH₃ adsorption-desorption apparatus60 is higher than the ammonia partial pressure in the warming-up heatstorage reactor 50 and the NH₃ flow pipe 62 due to adsorbed ammonia.Therefore, by making valves V1 and V2 attached to the NH₃ flow pipe 62in the opened state, ammonia gas can be supplied to the warming-up heatstorage reactor 50.

Due to the heat generation by supply of ammonia, the temperature of thewarming-up heat storage reactor 50 is raised. Since the heat absorptionand generation caused by the desorption and adsorption of ammonia in theadsorbent is based on a fixed reversible reaction, for example, byregulating the NH₃ partial pressure in the warming-up heat storagereactor 50 in a certain range, the temperature of the warming-up heatstorage reactor 50 is maintained at a desired temperature (a constanttemperature near 150° C.)

As the adsorbent, a porous body member can be used. The pore diameter ofthe porous body member is preferably 10 nm or smaller from the viewpointof more improving the reactivity of the fixation and desorption ofammonia by adsorption (preferably physical adsorption). The lower limitvalue of the pore diameter is preferably 0.5 nm from the viewpoint ofthe production suitability and the like. Also from the similarviewpoint, the porous body member is preferably a primary particleaggregate obtained by aggregating primary particles having an averageprimary particle diameter of 50 μm or smaller. The lower limit of theaverage primary particle diameter is preferably 1 μm from the viewpointof the production suitability and the like.

Examples of the adsorbent include, in addition to the activated carbonused in the present embodiment, mesoporous silica, zeolite, silica geland clay minerals. The activated carbon has a specific surface area byBET method of preferably 500 m²/g or larger and 2,500 m²/g or smaller,and more preferably 1,000 m²/g or larger and 2,500 m²/g or smaller. Theclay minerals may be non-bridged clay minerals, or may be bridged clayminerals. Examples of the clay mineral include sepiolite.

In the present invention, the kind of the adsorbent (preferably a porousbody member) can suitably be selected according to the pressure andtemperature of ammonia. The adsorbent preferably contains at least anactivated carbon from the viewpoint of more improving the reactivity ofthe fixation and desorption of ammonia by adsorption.

When the heat storage material to absorb and generate heat by transferof ammonia by using the adsorbent (preferably a physical adsorbent), thecontent ratio of the adsorbent in the heat storage material is, from theviewpoint of more highly maintaining the reactivity of the fixation anddesorption of ammonia, preferably 80% by volume or higher, and morepreferably 90% by volume or higher.

When the heat storage material using the adsorbent is utilized as amolded body, the heat storage material preferably contains, in additionto the adsorbent, a binder. The incorporation of the binder, sincemaking the shape of the molded body to be more easily maintained, moreimproves the reactivity of the fixation and desorption of ammonia byadsorption. The heat storage material may contain, as required, inaddition to the adsorbent and the binder, other components. Examples ofthe other components include heat-conductive inorganic materials such ascarbon fibers and metal fibers.

The binder is preferably a water-soluble binder. Examples of thewater-soluble binder include polyvinyl alcohols and trimethyl cellulose.

When the heat storage material is constituted by using the adsorbent andthe binder, the content ratio of the binder in the heat storage materialis, from the viewpoint of more effectively maintaining the shape of themolded body, preferably 5% by volume or higher, and more preferably 10%by volume or higher.

A molding method of the molded body is not particularly limited.Examples of the method include a method for molding, for example, a heatstorage material (or a slurry containing the heat storage material)containing an adsorbent (and as required, a binder and other components)by known molding means such as pressure molding or extrusion. Thepressure at the molding can be made to be, for example 20 to 100 MPa,and is preferably 20 to 40 MPa.

In the interior of the NH₃ depressurization heat storage reactor 70, achemical heat storage material as an ammonia fixation section to fixammonia is provided. The NH₃ depressurization heat storage reactor 70 isa low-temperature operation type heat storage reactor. The NH₃depressurization heat storage reactor 70 is connected to a midwaysection of the NH₃ flow pipe 62 through an NH₃ flow pipe 72. The NH₃depressurization heat storage reactor 70 communicates with thewarming-up heat storage reactor 50 and the NH₃ adsorption-desorptionapparatus 60 through the NH₃ flow pipes 62 and 72.

The NH₃ depressurization heat storage reactor 70, after the warming-uptermination of the purification catalyst, recovers ammonia gas byadsorbing ammonia gas present in the warming-up heat storage reactor 50and the NH₃ flow pipe 62. That is, after the warming-up termination ofthe purification catalyst, when the warming-up heat storage reactor 50is further heated along with a temperature rise of the warming-upexhaust gas, NH₃ adsorbed by the warming-up heat storage reactor 50(heat storage material 52) is desorbed from the heat storage reactor 50,and desorbed NH₃ is returned to the NH₃ adsorption-desorption apparatus60 through the NH₃ flow pipe 62 and again adsorbed by the NH₃adsorption-desorption apparatus 60. Thereby, the regeneration of the NH₃adsorption-desorption apparatus 60 is started. NH₃ is, however, liableto remain in the warming-up heat storage reactor 50 and in the NH₃ flowpipe 62. In the present embodiment, the NH₃ depressurization heatstorage reactor 70 is a low-temperature operation type heat storagereactor equipped with the heat storage material exhibiting a high NH₃adsorption power at a lower temperature than the NH₃adsorption-desorption apparatus 60. Hence, the remaining NH₃ is removedand the ammonia pressure in the warming-up heat storage reactor 50 andthe NH₃ flow pipe 62 can be reduced.

The heat storage material provided in the NH₃ depressurization heatstorage reactor 70 may be a heat storage material using chemicaladsorption or physical adsorption as long as the material is able toreduce the ammonia pressure in the reactor and the piping. The NH₃depressurization heat storage reactor 70 can be equipped with, but notlimited to the chemical heat storage material used in the presentembodiment, another chemical heat storage material, or a physicaladsorbent to fix NH₃ by physical adsorption.

For the ammonia fixation section of the NH₃ depressurization heatstorage reactor 70, a chemical adsorbent is suitably used from theviewpoint of rapidly reducing the ammonia pressure in the apparatusesand piping. The use of the chemical heat storage material, since thechemical heat storage material has a high heat storage density and isexcellent in the adsorbability of ammonia gas, can ensure a higher NH₃adsorbability in the NH₃ depressurization heat storage reactor 70 thanin the NH₃ adsorption-desorption apparatus 60.

The chemical heat storage material of the ammonia fixation section ispreferably a metal chloride. The chemical heat storage material is morepreferably, for example, a chloride of an alkali metal, a chloride of analkaline earth metal, or a chloride of a transition metal. Examples ofthe chemical heat storage material include the compounds similar tothose for the warming-up heat storage reactor 50. As described above,the chemical heat storage material causes an exothermic reaction at theammonia adsorption, and causes an endothermic reaction at the ammoniadesorption. The NH₃ depressurization heat storage reactor 70 using thechemical heat storage material adsorbs ammonia by being regulated to atemperature easily generating heat, and discharges ammonia by beingheated to thereby regenerate the heat storage material. The chemicalheat storage material of the NH₃ depressurization heat storage reactor70 is suitably BaCl₂, CaCl₂ or SrCl₂ in the point of ensuring a goodadsorption effect of ammonia in a low thermal energy. The details of thephysical adsorbents have already been described.

The chemical heat storage material of the NH₃ depressurization heatstorage reactor 70 according to the present embodiment is molded bypress-molding a powder of calcium chloride (CaCl₂). The use of CaCl₂ canlead to such an anticipation that the NH₃ depressurization heat storagereactor 70 has a higher NH₃ adsorbability than the warming-up heatstorage reactor 50 using MgCl₂ in a low-temperature region. When CaCl₂is used, the adsorption-desorption of ammonia is carried out accordingto the following reversible reaction (2), accompanied by heat generationand absorption.

CaCl₂.2NH₃+6NH₃

CaCl₂.8NH₃ +Q ²[kJ]  (2)

For molding, a molding method similar to that for the chemical heatstorage material used for the warming-up heat storage reactor 50 can beapplied.

As shown in FIG. 2, in the present embodiment, the NH₃ depressurizationheat storage reactor 70 is connected to the warming-up heat storagereactor 50 and the NH₃ adsorption-desorption apparatus 60 through theNH₃ flow pipes 62 and 72. Ammonia desorbed from the warming-up heatstorage reactor 50 by a temperature rise after the warming-uptermination of the warming-up heat storage reactor 50 is again adsorbedto the NH₃ adsorption-desorption apparatus 60, and thereafter, by makinga valve V3 attached to the NH₃ flow pipe 72 to be in the opened state,ammonia gas remaining in the warming-up heat storage reactor 50 and theNH₃ flow pipes 62 and 72 can be recovered. It can be thereby avoidedthat ammonia is decomposed in DPF by being heated to 400° C. or higherby a high-temperature exhaust gas flowed when PM is subjected to acombustion treatment in DPF.

In the present embodiment, the description has been made by taking as anexample a case where MgCl₂, which is a chemical heat storage material,is used as the heat storage material 52 of the warming-up heat storagereactor 50, and CaCl₂, which is a chemical heat storage material, isused as the heat storage material of the NH₃ depressurization heatstorage reactor 70, but a case is not limited thereto, and may be acombination of the heat storage material 52 of the warming-up heatstorage reactor 50 containing MgCl₂, MnCl₂, CoCl₂, NiCl₂, MgBr₂ or MgI₂and the heat storage material of the NH₃ depressurization heat storagereactor 70 containing a physical adsorbent. It is particularlypreferable from the viewpoint of ensuring the heat storage density inthe warming-up heat storage reactor 50 and improving the ammoniaadsorbability when the ammonia pressure is reduced that the warming-upheat storage reactor 50, which is the warming-up section, containsMgCl₂, MnCl₂, CoCl₂, NiCl₂, MgBr₂ or MgI₂ as the heat storage material52, and the NH₃ depressurization heat storage reactor 70 contains BaCl₂,CaCl₂ or SrCl₂ as the heat storage material.

The temperature range where the catalytic reactor is operated can bemade to be in the range of −30° C. or higher and 250° C. or lower. Theammonia pressure (operating pressure) in the catalytic reactor can bemade to be, for example, in the range of 0.1 atm or higher and 10 atm orlower.

Then, operation of the catalytic reactor 20 according to the presentembodiment will be described by reference to FIGS. 5 to 9. When theignition switch (IG switch) is turned on and the diesel engine isstarted, or at the starting of the diesel engine, the purificationcatalyst of the catalytic reaction apparatus 40 is in a low temperature.As shown in FIG. 5, the valves V1 and V2 are opened to thereby introduceammonia gas from the NH₃ adsorption-desorption apparatus 60 to thewarming-up heat storage reactor 50. The NH₃ adsorption-desorptionapparatus 60 is in such a state in which ammonia is beforehand adsorbed.Since the differential pressure between the ammonia pressure in the NH₃adsorption-desorption apparatus 60 and the ammonia pressure in the NH₃flow pipe 62 and the warming-up heat storage reactor 50 is large,ammonia gas is transferred to the warming-up heat storage reactor 50through the NH₃ flow pipe 62 by the differential pressure by followingthe opening of the valves. As shown in FIG. 3, in the warming-up heatstorage reactor 50, the ammonia gas introduced from the NH₃ inlet port58 flows in the porous body member 54 and contacts each of the heatstorage materials 52.

Each of the heat storage materials, as indicated by the reversiblereaction (1), reacts with ammonia and generates heat. By utilizing thisheat generation, the purification catalyst is warmed up to apredetermined temperature (for example, 150° C.). At this time, theexhaust gas of, for example, 100° C. discharged from the diesel engineis discharged after being purified with the purification catalyst of,for example, 150° C.

The NH₃ adsorption-desorption apparatus 60 according to the presentembodiment does not necessarily need a mechanism of heating the physicaladsorbent. In the NH₃ adsorption-desorption apparatus 60, however, aheater, which heats the physical adsorbent by heat exchange between thephysical adsorbent and a heat medium through flowing the heat mediumsuch as water, alcohol, or mixture thereof, may be arranged as a heatexchanger, from the viewpoint of more effectively carrying outdesorption of ammonia in a low-temperature environment such as below thefreezing point.

When the purification catalyst is warmed up to a target temperature (forexample, 150° C.), the warming-up is terminated. After the terminationof the warming-up, the chemical heat storage material of the warming-upheat storage reactor 50 is also heated along with the temperature riseof the purification catalyst due to the temperature rise of the exhaustgas. As shown in FIG. 6, if the exhaust gas of, for example, 200° C. isdelivered to the catalytic reaction apparatus 40 with the valves V1 andV2, which are maintained in the opened state, NH₃ coordinated (adsorbed)to MgCl₂ is desorbed. The ammonia pressure in the warming-up heatstorage reactor 50 thereby becomes higher than the ammonia pressure inthe NH₃ adsorption-desorption apparatus 60 and the NH₃ flow pipe 62. Theammonia gas returns to the NH₃ adsorption-desorption apparatus 60through the NH₃ flow pipe 62 due to the differential pressure. In such amanner, the ammonia gas adsorbed by the warming-up heat storage reactor50 (heat storage material 52) at the warming-up is desorbed by thetemperature rise of the purification catalyst along with the temperaturerise of the exhaust gas, and again adsorbed to the NH₃adsorption-desorption apparatus 60. As a result, the NH₃adsorption-desorption apparatus 60 is regenerated (heat storage) forpreparation for the succeeding warming-up. Since the NH₃ desorption atthis time is an endothermic reaction, the temperature of the exhaust gasbecomes lower than the temperature of the exhaust gas at theintroduction. When the regeneration is completed, the valve V2 isclosed. The regeneration completion can be determined from the ammoniapressure in the NH₃ adsorption-desorption apparatus 60 caused by theammonia adsorbed in the NH₃ adsorption-desorption apparatus 60.

After the completion of the regeneration (heat storage) of the NH₃adsorption-desorption apparatus 60, ammonia of a high pressure (forexample, 4 atm) still remains in the warming-up heat storage reactor 50and the NH₃ flow pipe 62 and a part of the NH₃ flow pipe 72 (a partexcluding the section between the valve V3 and the NH₃ depressurizationheat storage reactor 70). At this time, since the differential pressurebetween the NH₃ adsorption-desorption apparatus 60 and the NH₃ flow pipe62 is small, all of the ammonia gas in the NH₃ flow pipe 62 and theabove-mentioned part of the NH₃ flow pipe 72 does not completely returnto the NH₃ adsorption-desorption apparatus 60. Therefore, as shown inFIG. 7, the valve V3 is opened with the valve V2 being closed to therebyconnect the warming-up heat storage reactor 50 and the NH₃depressurization heat storage reactor 70. At this time, the valve V1remains in the opened state. Thereby, ammonia gas remaining in thereactors and the pipes is introduced to the NH₃ depressurization heatstorage reactor 70, which is a low-temperature operation type heatstorage apparatus capable of coordination-bonding and adsorbing ammoniaat a low pressure, and adsorbed to the chemical heat storage material.Since the adsorption is an exothermic reaction, at this time, by coolingthe chemical heat storage material in the NH₃ depressurization heatstorage reactor 70 by the outside air, the adsorption reaction(exothermic reaction) of ammonia is progressed in a favorable manner.Ammonia in the warming-up heat storage reactor 50 and the NH₃ flow pipe62 and the above-mentioned section of the NH₃ flow pipe 72 is thusrapidly removed. Thereafter, among the valves in the opened state, atleast the valve V1 is closed for the purpose of not undergoing theinfluence of the temperature change. As shown in FIG. 8, in the presentembodiment, both of the valves V1 and V3 are closed.

The NH₃ depressurization heat storage reactor 70 according to thepresent embodiment is further equipped with a flow pipe to flow a heatmedium, and a heater 74, which heats the chemical heat storage materialby heat exchange between the chemical heat storage material and the heatmedium through the flow of the heat medium, is provided as a heatexchanger. The heater 74 is equipped with a circulation system utilizinga flow pipe to circulate the heat medium. The flow pipe is provided witha heater (not shown in Fig.) that heats the heat medium to a desiredtemperature. As the heat medium, water, an organic solvent (an alcoholsuch as ethanol, a glycol such as ethylene glycol, or the like), or amixture thereof can be used.

In the automobile according to the present embodiment equipped with thediesel engine, a treatment to regenerate the DPF is carried out byburning and removing PM deposited on the DPF. In this case, since theregeneration treatment of the PM removal filter (DPF) 80 is carried outat a high temperature of, for example, 600° C., as shown in FIGS. 1 and8, a high-temperature gas of 600° C. is flowed also to the catalyticreaction apparatus 40 arranged upstream of the DPF 80 in the exhaust gasflow direction. Therefore, the warming-up heat storage reactor 50 isexposed to a high-temperature environment of 600° C. At this time, sincethe warming-up heat storage reactor 50 and a part of the NH₃ flow pipe62 connected thereto are in such a state in which remaining ammonia hasalready been removed, the decrease of the warming-up function by thepyrolysis of the remaining ammonia is prevented. The warming-up functionand the purification function of the exhaust gas of the catalyst in thegas purifier 30 are thereby enabled to be stably maintained over a longperiod.

After the remaining ammonia gas is removed and the valves V1 to V3 areclosed as described above, as shown in FIG. 9, the valves V2 and V3 areopened to thereby connect the NH₃ adsorption-desorption apparatus 60with the NH₃ depressurization heat storage reactor 70. The valve V1remains in the closed state. At this time, the chemical heat storagematerial in the NH₃ depressurization heat storage reactor 70 is heatedto about 70° C. by the heater 74 located in the NH₃ depressurizationheat storage reactor 70 as described before. The physical adsorbent inthe NH₃ adsorption-desorption apparatus 60, since generating heat byadsorption of ammonia, is cooled by being exposed to the outside air.The chemical heat storage material (CaCl₂) built in the NH₃depressurization heat storage reactor 70 is able to desorb NH₃ at a lowtemperature of about 70° C. (the reversible reaction (2):CaCl₂.8NH₃+Q²→CaCl₂.2NH₃+6NH₃). Ammonia gas is transferred and againadsorbed to the NH₃ adsorption-desorption apparatus 60 by thedifferential pressure between the ammonia pressure in the NH₃depressurization heat storage reactor 70 and the ammonia pressure in theNH₃ adsorption-desorption apparatus 60 and the NH₃ flow pipe 72 at thistime. The NH₃ adsorption-desorption apparatus 60 is thereby regeneratedinto the initial state in which ammonia is adsorbed, and the warming-upsimilar to the above can be carried out repeatedly.

As described above, by removing ammonia gas in the warming-up heatstorage reactor 50 and the NH₃ flow pipe 62 by the NH₃ depressurizationheat storage reactor 70 provided separately from the NH₃adsorption-desorption apparatus 60 at a predetermined timing when theammonia gas is exposed to a high temperature, the warming-up function bythe warming-up heat storage reactor 50 can be stably maintained over along period, and the catalytic activity of the purification catalyst canbe stably maintained irrespective of the usage environment.

Then, a control routine by a controller 100, which is a control sectionfor controlling the diesel engine (internal combustion engine) accordingto the present embodiment, will be described. In the control routine,particularly a warming-up control routine for removing ammonia gas willbe mainly described by reference to FIG. 10, in association withwarming-up of the catalytic reaction apparatus 40 in the catalyticreactor 20 and the execution of the DPF regeneration mode forregenerating the DPF by burning and removing PM deposited on the DPFafter the warming-up.

When the ignition switch (IG switch) is turned on to thereby turn on thepower source of the controller 100, the system is started, and thewarming-up control routine for controlling the warming-up in thecatalytic reactor 20 is executed. The starting of the system may be madeautomatically or manually.

On execution of the process of the present routine, it is firstdetermined whether the purification function by the purificationcatalyst of the catalytic reaction apparatus 40 normally works, that is,whether warming-up of the purification catalyst is necessary. That is,in step 100, the temperature of the catalyst is detected by thetemperature detection sensor 44 attached to the purification catalyst,and it is determined whether the detected temperature is lower than apredetermined temperature T (for example, 180° C.) at which thepurification of the exhaust gas can be carried out.

In step 100, when it is determined that the detected temperature islower than the predetermined temperature T, and has not reached atemperature at which the purification of the exhaust gas can be reliablycarried out, since the temperature of the catalyst needs to be raised,the process proceeds to step 120. In contrast, when it is determinedthat the detected temperature is the predetermined temperature T orhigher, since the temperature of the catalyst has already reached thetemperature at which the purification of the exhaust gas is reliablycarried out, and the purification catalyst is able to remove deleteriousgases, the present routine process is terminated.

In step 120, the ammonia pressure of the NH₃ adsorption-desorptionapparatus 60 is measured for preparation for warming-up, and it isdetermined whether the ammonia pressure exceeds a predetermined pressureP, that is, whether ammonia is in such a state in which the ammonia ofan amount necessary for warming-up is adsorbed in the NH₃adsorption-desorption apparatus 60. In step 120, when it is determinedthat the ammonia pressure exceeds the pressure P, since the state is ina state of being able to start warming-up, in the following step 180,the valves V1 and V2 are opened. At this time, the valve V3 remains inthe closed state.

In contrast, when it is determined in step 120 that the ammonia pressureis the pressure P or lower, for example, for the reason that theregeneration of the NH₃ adsorption-desorption apparatus 60 was notcompleted at the preceding warming-up, since ammonia of an amountnecessary for warming-up cannot be ensured, in step 140, after thevalves V1 and V3 are opened to thereby make remaining ammonia to beadsorbed to the NH₃ depressurization heat storage reactor 70, the valveV1 is closed and the valves V2 and V3 are opened. In the following step160, the heater 74 is turned on to thereby heat the chemical heatstorage material of the NH₃ depressurization heat storage reactor 70 bythe heater 74. Thereby, ammonia adsorbed in the NH₃ depressurizationheat storage reactor 70 is desorbed from the NH₃ depressurization heatstorage reactor 70, and the desorbed ammonia is transferred to the NH₃adsorption-desorption apparatus 60. Thereafter, again in step 120, it isdetermined whether the ammonia pressure exceeds the predeterminedpressure P. Until it is determined that the ammonia pressure exceeds thepredetermined pressure P, steps 120, 140 and 160 are similarly repeated.When it is determined that the ammonia pressure exceeds the pressure P,the process proceeds to the following step 180, and the valves V1 and V2are opened.

In the above manner, by making the valves V1 and V2 to be in the openedstate, as shown in FIG. 5, ammonia gas is introduced from the NH₃adsorption-desorption apparatus 60 to the warming-up heat storagereactor 50 to thereby start warming-up of the catalytic reactionapparatus 40 by the warming-up heat storage reactor 50.

At this time, by maintaining the ammonia pressure in the system wherethe valves V1 and V2 are in the opened state, at a predeterminedpressure value P² (P²<P), the temperature of the purification catalystis self-regulated to a predetermined temperature (for example, 150° C.),which is a target temperature.

After the purification catalyst is warmed up to the target temperature(for example, 150° C.), also the temperature of the purificationcatalyst is raised along with the temperature rise of the exhaust gas,and also the temperature of the chemical heat storage material of thewarming-up heat storage reactor 50 is resultantly raised. As shown inFIG. 6, with the valves V1 and V2 being maintained in the opened state,when the exhaust gas of, for example, 200° C. is flowed in the catalyticreaction apparatus 40, NH₃ coordinated (adsorbed) to MgCl₂ (chemicalheat storage material) of the warming-up heat storage reactor 50 isdesorbed. At this time, the ammonia pressure in the warming-up heatstorage reactor 50 becomes higher than the ammonia pressure in the NH₃adsorption-desorption apparatus 60 and the NH₃ flow pipe 62, and ammoniagas returns to the NH₃ adsorption-desorption apparatus 60 through theNH₃ flow pipe 62 by the differential pressure, and the regeneration isstarted.

Under such a situation, in step 200, it is determined whether theammonia pressure in the NH₃ adsorption-desorption apparatus 60 exceeds apredetermined pressure value P¹ (P¹<P) indicating that a certain orgreater amount of NH₃ has been adsorbed. In step 200, when it isdetermined that the ammonia pressure in the NH₃ adsorption-desorptionapparatus 60 exceeds the pressure value P¹, since the regeneration ofthe NH₃ adsorption-desorption apparatus 60, which automatically proceedsalong with the temperature rise of the catalyst is terminated, in step220, the valve V2 is closed, and the valve V3 is opened. The valve V1remains in the opened state. The interior of the warming-up heat storagereactor 50 and the interior of the NH₃ flow pipe 62 are in a state inwhich high-pressure ammonia remains. By opening the valve V3, theremaining ammonia is adsorbed and rapidly removed by the low-temperatureoperation type NH₃ depressurization heat storage reactor 70. In such amanner, the ammonia pressure in the warming-up heat storage reactor 50and the NH₃ flow pipe 62 is reduced.

In contrast, in step 200, when it is determined that the ammoniapressure in the NH₃ adsorption-desorption apparatus 60 is lower than thepressure value P¹, since the warming-up has not proceeded, or theregeneration of the NH₃ adsorption-desorption apparatus 60 after thewarming-up has not proceeded, the process returns to step 180, and steps180 and 200 are similarly repeated.

In the following step 240, it is determined whether the DPF regenerationmode for burning and removing PM deposited on the DPF needs to beexecuted. In step 240, when it is determined that the DPF regenerationmode needs to be executed, in the following step 260, the valves V1 andV3 are closed in order to avoid pyrolysis of ammonia due to the flow ofthe exhaust gas of a high temperature at the DPF regeneration. Incontrast, in step 240, when it is determined that the DPF regenerationmode does not need to be executed, since there is no fear of thepyrolysis of ammonia, the process proceeds to step 340, and all thevalves (V1 to V3) are closed and the process of the present routine isterminated.

After the valves V1 and V3 are closed in step 260 (also the valve V2 isin the closed state), in step 280, the NH₃ depressurization heat storagereactor 70 is heated by the heater 74 in order to return the remainingammonia adsorbed in the NH₃ depressurization heat storage reactor 70 tothe NH₃ adsorption-desorption apparatus 60, irrespective of before orafter the execution of the DPF regeneration mode. Further in step 300,the valves V2 and V3 are opened to connect the NH₃ adsorption-desorptionapparatus 60 with the NH₃ depressurization heat storage reactor tothereby return the remaining ammonia to the NH₃ adsorption-desorptionapparatus 60.

In the following step 320, it is determined whether the ammonia pressurein the NH₃ adsorption-desorption apparatus 60 is restored to apredetermined value P³ or higher, which can be regarded to besubstantially the same as the predetermined pressure P before the startof the warming-up. When it is determined that the ammonia pressure inthe NH₃ adsorption-desorption apparatus 60 at this time point is thepredetermined value P³ or higher, since the regeneration of the NH₃adsorption-desorption apparatus 60 is substantially completed, all thevalves (V1 to V3) are closed in step 340, and the process of the presentroutine is terminated.

In step 320, when it is determined that the ammonia pressure in the NH₃adsorption-desorption apparatus 60 is lower than the predetermined valueP³, it is assumed that ammonia gas still remains in the NH₃depressurization heat storage reactor 70 and the NH₃ flow pipe 62. Sincethe regeneration of the NH₃ adsorption-desorption apparatus 60 is notcompleted, by repeating step 320 until the ammonia pressure reaches thepredetermined value P³ or higher, the completion of the regeneration iswatched and waited. Thereafter, when it is determined that the ammoniapressure in the NH₃ adsorption-desorption apparatus 60 is thepredetermined value P³ or higher, the process proceeds to step 340, andall the valves are closed, and the process of the present routine isthereafter terminated.

In the above embodiment, the case where MgCl₂ and CaCl₂ are used as thechemical heat storage materials, and the activated carbon, which is aphysical adsorbent, is used as the adsorbent capable of adsorbingammonia has been mainly described. However, the chemical heat storagematerials and the adsorbent are not limited thereto. If other chemicalheat storage materials and adsorbents described above other than MgCl₂,CaCl₂ and the activated carbon are used, the same advantages as in theabove embodiment are attained.

Further in the above embodiment, the case where the chemical heatstorage material is used as the ammonia fixation section of the NH₃depressurization heat storage reactor 70 has been mainly described, buta physical adsorbent may be used in place of the chemical heat storagematerial. Also in this case, by making the adsorbability of ammonia ofthe ammonia fixation section of the NH₃ depressurization heat storagereactor 70 superior to that of the chemical heat storage material of thewarming-up heat storage reactor 50, the same advantages as in the aboveembodiment using the chemical heat storage material can be attained.

1. A catalytic reactor comprising: a catalytic reaction section having apurification catalyst for purifying gas; a warming-up section located ata position capable of heat-exchanging with the purification catalyst,and wherein the warming-up section has a chemical heat storage materialthat generates heat when ammonia is fixed and absorbs heat when ammoniais desorbed; an ammonia supply section having an adsorbent capable ofadsorbing ammonia, wherein the ammonia supply section transfers ammoniafrom and to the warming-up section by adsorption and desorption ofammonia; and an ammonia depressurization section that has an ammoniafixation section for fixing ammonia and reduces an ammonia partialpressure at least in the warming-up section after the desorption ofammonia from the chemical heat storage material.
 2. The catalyticreactor according to claim 1, wherein the adsorbent is a physicaladsorbent capable of physically adsorbing ammonia.
 3. The catalyticreactor according to claim 1, wherein the adsorbent has at least oneselected from the group consisting of activated carbon, mesoporoussilica, zeolite, silica gel, and clay minerals.
 4. The catalytic reactoraccording to claim 1, wherein the warming-up section has at least oneammonia supply port and a porous body member arranged between thechemical heat storage material and the ammonia supply port, and theporous body member is arranged such that ammonia supplied to thewarming-up section through the at least one ammonia supply port diffusesin the porous body member and contacts the chemical heat storagematerial.
 5. The catalytic reactor according to claim 1, wherein thechemical heat storage material comprises at least one of a metalchloride, a metal bromide, and a metal iodide.
 6. The catalytic reactoraccording to claim 5, wherein the metal chloride, the metal bromide, orthe metal iodide is selected from the group consisting of alkali metalchlorides, alkaline earth metal chlorides, transition metal chlorides,alkali metal bromides, alkaline earth metal bromides, transition metalbromides, alkali metal iodides, alkaline earth metal iodides, andtransition metal iodides.
 7. The catalytic reactor according to claim 1,wherein the chemical heat storage material comprises at least one ofMgCl₂, MnCl₂, CoCl₂, NiCl₂, MgBr₂ and MgI₂.
 8. The catalytic reactoraccording to claim 1, wherein the chemical heat storage material is afirst chemical heat storage material, and the ammonia fixation sectionhas a second chemical heat storage material that generates heat whenammonia is fixed and absorbs heat when ammonia is desorbed.
 9. Thecatalytic reactor according to claim 8, wherein the second chemical heatstorage material comprises at least one of BaCl₂, CaCl₂, and SrCl₂. 10.The catalytic reactor according to claim 1, wherein the ammoniadepressurization section has a heating section that heats the ammoniafixation section by heat-exchanging with the ammonia fixation sectionthrough flow of a heat medium.
 11. A vehicle comprising an internalcombustion engine and the catalytic reactor according to claim 1,wherein the catalytic reactor is adapted such that exhaust gasdischarged from the internal combustion engine flows into the catalyticreactor.
 12. The vehicle according to claim 11, wherein the internalcombustion engine is a diesel engine, and the vehicle further comprisesa carbonaceous substance purification section downstream of thecatalytic reactor in an exhaust gas flow direction.